Powder coating additive, powder coating composition containing said additive, and method for coating a substrate using said powder coating composition

ABSTRACT

A powder coating additive composition containing (a) a non-crosslinked product made by the reaction of an organic alcohol and a carboxylic acid or a reactive equivalent of the carboxylic acid; the product containing at least one ester functionality and at least one hydrocarbyl group of about 10 to about 100 carbon atoms; and (b) a fluoropolymer. The cured coatings exhibit lower coefficient of friction and substantial gloss retention.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to non-flatting and slip-enhancingcoating additives, powder coating compositions containing the additives,and to a process for coating a substrate using the powder coatingcomposition.

[0003] 2. Description of Related Art

[0004] Slip is the relative movement between two objects that are incontact with each other. If an object is moved along a surface, there isa resistance acting in a direction opposite the movement. The resistingforce is also called frictional force, friction resulting from theunevenness of the two surfaces in contact.

[0005] Coating systems, including powder coatings are susceptible todamage when in contact with solid objects. Paint films, for instance,can be easily damaged during drying, when they have not yet cured. Inthe case of baking enamels, damage can occur when the films have not yetcooled. In addition, scratches, which are discontinuities on surfaces,can cause attachment of air-borne contaminants and corrosive agentsleading eventually to corrosion problems. Powder coating systems arewell known to those skilled in the art. A common problem with manypowder coatings is that they are subject to mar or scratching.

[0006] Slip additives provide some degree of protection against suchdamages. For example, in automotive coating applications, they protectthe not fully hardened freshly applied enamels, and in can coatings,they protect the coating during filling and distribution.

[0007] The concepts of slip and mar (or scratch) resistance are veryclosely interrelated in that the same additive may perform bothfunctions-impart slip and provide scratch resistance; in addition theprinciple underlying both is the same. A hard object touching a paintfilm containing an additive can be deflected due to the surfacelubricity of the additive. This results in a greater apparent filmhardness or scratch resistance.

[0008] A slip additive should generally fulfill several requirements.The additive should migrate to the film surface during the dryingprocess, forming a film which not only adheres to the coating, but alsofavorably influences its flow and leveling properties. In addition, thisfilm should have lubricating qualities, expressed as the ability tocarry a load in a very thin layer.

[0009] Compounds based on silicone chemistry have been used as mar andslip additives for about 30 years. Examples of silicone-based slipadditives include polydimethylsiloxanes, polyoxyalkylenesiloxane(polysiloxane/polyether) copolymers, and polyoxyalkylenemethylalkylsiloxane copolymers.

[0010] The problem with many slip additives is that they reduce thegloss of the cured coating. The present invention provides enhanced slip(reduction of coefficient of friction) to cured powder coatings usefulin rendering the cured coatings more resistant to mar or scratch withoutan appreciable loss in gloss.

[0011] A detailed description describing the concept of slip and mar andthe developments of additives to improve scratch resistance and impartslip can be found in an article by F. Fink, et al., entitled“Development of New Additives to Improve Scratch Resistance and ImpartSlip To Solvent-Based Coating Systems” in Journal of CoatingsTechnology, Vol. 62, No. 791, December 1990.

[0012] U.S. Pat. No. 3,455,726, Mitchell, Jr. et al., Jul. 15, 1969,discloses an article comprising a paper substrate, a moisture resistantfilm of polymer, selected from the group consisting of vinylidenechloride polymers, polyethylene and polypropylene superimposed on saidsubstrate, and a slip coating on said film, said slip coating consistingessentially of a partial ester of a fatty acid and hexitol anhydride,including a polyoxyethylene derivative of said ester.

[0013] U.S. Pat. No. 4,289,828, Ota et al., Sep. 15, 1981, discloses amagnetic recording medium made by coating a base with a magnetic coatingmaterials which is a dispersion of magnetic particles in a binder ofsynthetic resins using a polyfunctional aromatic isocyanate as a curingagent, characterized by the addition of a sorbitan stearate type surfaceactive agent.

[0014] Japanese Laid-open Patent Publication No. 57-30119, Nishimatsu,Feb. 18, 1982, discloses a magnetic recording medium, comprising amagnetic paint containing a curing component and a surfactant andapplied on a substrate, wherein said curing component containsisophorone diisocyanate, and said surfactant contains a saturated fattyacid ester of sorbitan.

[0015] Japanese Patent Publication No. 63-44023, Suzuki et al., Sep. 2,1988 discloses a method of forming an coated layer of low frictionalresistance on the surface of an article such as a slip joint of a safetybelt connected to a car seat, said method comprising immersing thearticle to be coated in a fluidized bed containing 100 parts weight ofpolyamide powder and 0.01-5 parts by weight of PTFE powder, and therebyapplying the mixed powders as a low-friction coating on the surface ofthe particle.

SUMMARY OF THE INVENTION

[0016] The present invention relates to a composition, comprising: (a)at least one non-crosslinked product made by the reaction of an alcoholand a carboxylic acid or a reactive equivalent of said carboxylic acid;said product comprising at least one ester functionality and at leastone straight chain hydrocarbyl group of about 10 to about 100 carbonatoms; and (ii) at least one fluoropolymer. The invention also relatesto a powder coating composition comprising a film forming resin and anon-flatting slip-enhancing amount of an additive composition comprisingthe foregoing combination of (a) and (b), and to a method for a coatinga substrate using the foregoing powder coating composition.

DETAILED DESCRIPTION OF THE INVENTION

[0017] As used herein, the term “hydrocarbyl substituent” or“hydrocarbyl group” is used in its ordinary sense, which is well-knownto those skilled in the art. Specifically, it refers to a group having acarbon atom directly attached to the remainder of the molecule andhaving predominantly hydrocarbon character. Examples of hydrocarbylgroups include:

[0018] (1) hydrocarbon substituents, that is, aliphatic (e.g., alkyl oralkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, andaromatic-, aliphatic-, and alicyclic-substituted aromatic substituents,as well as cyclic substituents wherein the ring is completed throughanother portion of the molecule (e.g., two substituents together form analicyclic radical);

[0019] (2) substituted hydrocarbon substituents, that is, substituentscontaining non-hydrocarbon groups which, in the context of thisinvention, do not alter the predominantly hydrocarbon substituent (e.g.,halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto,alkylmercapto, nitro, nitroso, and sulfoxy);

[0020] (3) hetero substituents, that is, substituents which, whilehaving a predominantly hydrocarbon character, in the context of thisinvention, contain other than carbon in a ring or chain otherwisecomposed of carbon atoms. Heteroatoms include sulfur, oxygen, nitrogen,and encompass substituents as pyridyl, furyl, thienyl and imidazolyl. Ingeneral, no more than two, preferably no more than one, non-hydrocarbonsubstituent will be present for every ten carbon atoms in thehydrocarbyl group; typically, there will be no non-hydrocarbonsubstituents in the hydrocarbyl group.

[0021] A straight-chain hydrocarbyl group is a hydrocarbyl group that isfree from branching and ring structures. However, such a hydrocarbylgroup can still have a hetero substituent that does not alter thepredominantly hydrocarbon character of the hydrocarbyl group. Examplesof straight chain hydrocarbyl groups include n-butyl, n-octyl,n-dedodecyl and n-octadecyl groups.

[0022] The phrase “reactive equivalent” of a material means any compoundor chemical composition other than the material itself which reacts orbehaves like the material itself under the reaction conditions. Thusreactive equivalents of a carboxylic acid will include acid-producingderivatives such as an anhydride, an acyl halide, and mixtures thereofunless specifically stated otherwise.

[0023] The Alcohol (a)

[0024] Alcohols suitable for this invention include mono- or polyhydrichydrocarbon-based alcohols such as methanol, ethanol, the propanols,butanols, pentanols, hexanols, heptanols, octanols and decanols; alsoincluded are fatty alcohols and mixtures thereof, including saturatedalcohols such as lauryl, myristyl, cetyl, stearyl and behenyl alcohols,and unsaturated alcohols such as palmitoleyl, oleyl and eicosenyl.Higher synthetic monohydric alcohols of the type formed by the Oxoprocess (e.g., 2-ethylhexanol), by the aldol condensation, or byorganoaluminum-catalyzed oligomerization of alpha-olefins (especiallyethylene), followed by oxidation, are also useful. These higher alcoholsare discussed in detail under the title “Alcohols, Higher Aliphatic” inKirk-Othemer, Encyclopedia of Chemical Technology, Third Edition, Vol.1, pp. 716-754.

[0025] Also useful as organic alcohols are the alicyclic analogs of theabove-described alcohols; examples are cyclopentanol, cyclohexanol andcyclododecanol. Also useful are aliphatic substituted aromatic alcoholssuch as benzyl alcohol and 2-Naphthalenemethanol.

[0026] The preferred monhydric alcohols are the straight chain alcoholscontaining 10 to 24 carbon atoms.

[0027] Polyalcohols are also useful. These include ethylene, propylene,butylene, pentylene, hexylene and heptylene glycols wherein the hydroxygroups are separated by 2 carbon atoms; tri-, tetra-, penta-, hexa- andheptamethylene glycols and hydrocarbon-substituted analogs thereof(e.g., 2-ethyl-1,3-trimethylene glycol, neopentyl glycol), as well aspolyoxyalkylene compounds such as diethylene and higher polyethyleneglycols, tripropylene glycol, dibutylene glycol, dipentylene glycol,dihexylene glycol and diheptylene glycol, and their monoethers.

[0028] Also useful are sugar alcohols of the general formula

HOCH₂(CHOH)₁₋₅CH₂OH

[0029] such as glycerol, sorbitol, mannitol, ribitol, etc., and theirpartially esterified derivatives, and methylol polyols such aspentaerythritol and its oligomers (di- and tripentaerythritol, etc.),trimethylolethane and trimethylolpropane. Such compounds are describedunder the title “alcohol, Polyhydric” in Encyclopedia of ChemicalTechnology, Vol. 1, pp. 754-789.

[0030] The preferred polyalcohols are alcohols which comprise 2 to 10hydroxyl groups, more preferably 2 to 6 hydroxyl groups (e.g., ethyleneglycol, glycerol, trimethylolethane, trimethylolpropane,pentaerythritol, sorbitol, sorbitan, mannitol, ribitol, and inositol).

[0031] The Carboxylic Acid (a)

[0032] The carboxylic acids used to make the non-crosslinked product (a)of this invention can be mono-, di-, or polycarboxylic acids,represented by the formula B—(COOH)_(z), or reactive equivalentsthereof, wherein B is a direct link between two COOH groups, a mono-,di-, or a multivalent organic radical, and z represents the number ofcarboxyl groups. Preferably z is 1-10, more preferably 1-4. Thecarboxylic acids include aliphatic and aromatic carboxylic acids as wellas polycarboxylic acid compounds having multiple carboxylic acidfunctionalities or reactive equivalents thereof, such as esters,anhydrides or acyl halides. Monocarboxylic acids which may be used havethe formula RCOOH, wherein R is a hydrocarbyl group, preferably analiphatic group. Preferably R contains from 1 to 50 carbon atoms.Examples of aliphatic carboxylic acids include formic acid, acetic acid,propanoic acid, butanoic acid, decanoic acid, myristic acid, palmiticacid, oleic acid, stearic acid, isostearic acid, lauric acid, caprylicacid, capric and behenic acid. In an especially preferred embodiment,the carboxylic acid is a straight chain saturated 18 carbon carboxylicacid, namely stearic acid.

[0033] Also included among monocarboxylic acids are hydroxy-substitutedmonocarboxylic acids, such as 12-hydroxystearic acid and ricinoleic acid(castor oil acid).

[0034] Compounds useful as the di- or polycarboxylic acid in thisinvention can be selected from any aromatic, aliphatic orcycloaliphatic, straight chain or branched chain, saturated orunsaturated dicarboxylic acid which have at least 2 carbon atoms, andmore preferably 3 to 40 carbon atoms. Examples of these are oxalic acid,malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,suberic acid, sebacic acid, azelaic acid, undecanedioic acid,1,11-undecanedicarboxylic acid, dodecanedioic acid, hexadecanedioicacid, docosanedioic acid, maleic acid, fumaric acid and the like eitheralone or mixtures thereof. The term “dicarboxylic acid” is also used toinclude hydroxy substituted dicarboxylic acids. Representative ofhydroxy substituted dicarboxylic acids are tartaric acid, citric acidand hydroxyisopthalic acid.

[0035] Dicarboxylic acids can also include the substituted succinicacids represented by the formula

R—CH(COOH)CH₂COOH

[0036] wherein R is a hydrocarbyl group, including an olefinpolymer-derived group formed by polymerization of such monomers asethylene, propylene, 1-butene, isobutene, 1-pentene, 2-pentene,1-hexene, and 3-hexene. Such groups usually contain 30 to 200, moreoften up to about 100 carbon atoms. Reactive equivalents of saiddicarboxylic acids include succinic anhydrides of the formula

[0037] wherein R is a hydrocarbyl group, including an olefin-polymerderived group as disclosed for the succinic acid above.

[0038] Also useful are oligomers of fatty acids which are substantiallycomprised of dimerized fatty acids. They are normally called “dimeracids”, and are made by the thermal coupling of unsaturated vegetableacids. They are available from Emery, Westvaco, Henkel, Unichema andother companies. Trade names of these dimer acids include Empol™ fromHenkel Corporation, and Pripol™, from Unichema International.Illustrative examples of branched dimer acids are Empol™ 1004, Empol™1008, Empol™ 1018, Empol™ 1016. Dimer acids are described in U.S. Pat.Nos. 2,482,760, 2,482,761, 2,731,481, 2,793,219, 2,964,545, 2,978,468,3,157,681, and 3,256,304.

[0039] In addition to the dicarboxylic acids, acids containing more thantwo carboxylic acid groups are also useful. Representative examples ofthese polybasic acids are trimellitic acid, trimesic acid, citric acid,1,2,3,4-butanetetracarboxylic acid and the like. Polymerized polybasicacids which contain more than two carboxylic acid groups are alsoincluded in the definition of polybasic acids. The polymeric polybasicacids with 3 carboxylic acid groups are known as “trimer acids”. Thesetrimer acids are commercially available under the trade name Empol™ fromHenkel Corporation-Emery Group, and Unidyme™ from Union CampCorporation. Representative examples of these trimer acids are Empol™1040, Empol™ 1041. Polybasic acids which are mixtures of di, tri, tetra,penta, and hexacarboxylic acids are also useful for this invention.

[0040] Polyacid reaction products of unsaturated vegetable acids withacrylic acid and maleic anhydride are available from Westvaco under theproduct names Diacid™ 1550 and Tenax™ 2010, respectively.

[0041] The Reaction Product of the Alcohol and the Carboxylic Acid (a)

[0042] The reaction product (b) of the alcohol and the carboxylic acidof the present invention contains at least one ester functionality, andat least one straight chain hydrocarbyl group of 10 to 100 carbon atoms.In one embodiment, the reaction product of the alcohol and thecarboxylic acid has 1 to 4 ester functionalities. Preferably thestraight chain hydrocarbyl group will have 10 to 50 carbon atoms, andmore preferably 12 to 24 carbon atoms. The straight chain hydrocarbylgroup can come from either the carboxylic acid or the alcohol.Furthermore, the reaction product of the alcohol and the carboxylic acidshould not be the result of cross-linking or polymerization reactionbetween two molecules, each having multiple hydroxy or carboxylfunctionalities. Thus, both the alcohol and the carboxylic acid shouldnot at the same time contain reactive functionalities greater than two.

[0043] In one embodiment, the product (a) of this invention is ethyleneglycol distearate; in one embodiment, the product is glyceroldistearate; in one embodiment the product is pentaerythritoltetrastearate.

[0044] In one embodiment, the product (a) of this invention is asorbitan ester.

[0045] The sorbitan esters include sorbitan fatty acid esters whereinthe fatty acid component of the ester comprises a carboxylic acid of 10to 100 carbon atoms, and in one embodiment 12 to 24 carbon atoms.Sorbitan is a mixture of anhydrosorbitols, principally 1,4-sorbitan andisosorbide:

[0046] Sorbitan, (also known as monoanhydrosorbitol, or sorbitolanhydride) is a generic name for anhydrides derivable from sorbitol byremoval of one molecule of water. The sorbitan fatty acid esters of thisinvention are a mixture of partial esters of sorbitol and its anhydrideswith fatty acids. These sorbitan esters can be represented by thestructure below which may be any one of a monoester, diester, triester,tetraester, or mixtures thereof.

[0047] In the above formula, each Z independently denotes a hydrogenatom or C(O)R—, and each R mutually independently denotes a hydrocarbylgroup of 9 to 99 carbon atoms, more preferably 11 to 23 carbon atoms.Examples of sorbitan esters include sorbitan stearates and sorbitanoleates, such as sorbitan stearate (i.e., monostearate), sorbitandistearate, sorbitan tristearate, sorbitan oleate and sorbitansesquioleate. In one embodiment, the sorbitan ester is sorbitantristearate. Sorbitan esters are available commercially under thetradenames Spans™ and Arlacels™ and are also sold by Calgene ChemicalCompany.

[0048] The sorbitan esters also include polyoxyalkylene sorbitan esterswherein the alkylene group has 2 to 24 carbon atoms. Thesepolyoxyalkylene sorbitan esters can be represented by the structure

[0049] wherein each R independently is an alkylene group of 2 to 24carbon atoms; R¹ is a hydrocarbyl group of 9 to 99 carbon atoms, morepreferably 11 to 23 carbon atoms; and w, x, y, and z represent thenumber of repeat oxyalkylene units. For example ethoxylation of sorbitanfatty acid esters leads to a series of more hydrophilic surfactants,which is the result of hydroxy groups of sorbitan reacting with ethyleneoxide. One principal commercial class of these ethoxylated sorbitanesters are those containing 5 to 80 ethylene oxide units. They aremarketed by Calgene Chemical under the name “Polysorbate”. Typicalexamples are polyoxyethylene (hereinafter “POE”) (20) sorbitantristearate (Polysorbate 65) and POE (20) sorbitan trioleate(Polysorbate 85), POE (5) sorbitan monooleate (Polysorbate 81), and POE(80) sorbitan monooleate (Polysorbate 80). As used in this terminology,the number within the parentheses refer to the number of ethylene oxideunits present in the composition. The preferred sorbitan ester for thepresent invention is sorbitan tristearate, presently sold by CalgeneChemical Company as “Calgene STS”. Preferably, the alkylene group of thepolyoxyalkylene sorbitan esters is an alkylene group of 2 to 4 carbonatoms, i.e., it is selected from the group consisting of ethylene,propylene, butylene, and mixtures thereof.

[0050] The Fluoropolymer (b)

[0051] One component of the composition of the present invention is afluoropolymer. This polymer is blended with component (a) to form theadditive composition of the present invention.

[0052] The fluoropolymer (b) includes polymers produced from alkenes inwhich one or more hydrogens have been replaced by fluorine. Importantfluoropolymers include polytetrafloroethylene (PTFE), having thetetrafluoroethylene repeat unit (—CF₂CF₂—)_(n),polychlorotrifluoroethylene (PCTFE), having the repeat unit(—CF₂CFCl—)_(n), poly(vinyl fluoride) (PVF), having the repeat unit(—CF₂CHF—)_(n), poly(vinylidene fluoride) (PVDF), having the repeat unit(—CH₂CF₂—)_(n), copolymers of tetrafluoroethylene with ethylene,perfluoroproyl vinyl ether, and perfluoropropylene; and the copolymersof ethylene and chlorotrifluoroethylene. In one embodiment, thefluoropolymer (b) is a homopolymer of tetrafluoroethylene. The PTFE maybe virgin PTFE, radiated PTFE, or recycled/radiated PTFE. Suitableexamples of PTFE homopolymers include those available from Dupont underthe name “ZONYL™” fluoroadditives, from Hoechst and Dyneon under thename “HOSTAFLON™” PTFE, and from ICI under the name “FLUON™”. Specificexamples of these include ZONYL™ MP 1000, MP 1100, MP 1200, MP 1600N;HOSTAFLON™ TF 1620, TF 1641, TF 1645, TF 9201, TF 9202, TF 9205, TF X9207; and FLUON™ FL 1700.

[0053] The “ZONYL™” fluoropolymers are finely divided white powders ofPTFE. The properties of several of these are summarized in the tablebelow. Specific Average Surface Bulk Area Density Melting Peak ParticleSize (m²/g) ZONYL (g/L) Temperature Distribution (μm) (Nitrgoen Fluoro-(ASTM (° C./° F.) (Volume Basis) Ab- polymer D4894) (ASTM D4894) (LaserMicrotrac) sorption) MP 1000 500 325 ± 5/617 10% < 3  7-10 Avg. 12 90% <30 MP 1200 450 325 ± 5/617  10% < 1.0 1.5-3   Avg. 3 90% < 9  MP 1400425 325 ± 5/617 10% < 3  1.5-3   Avg. 10 90% < 20 MP 1500J 425 330 ±5/626 10% < 10 8-12 Avg. 20 90% < 35 MP 1600N 350 325 ± 5/617 Avg. 128-12

[0054] The “HOSTAFLON™” fluoropolymers are white, fine-particle powdersof low molecular weight PTFE. They are produced by direct polymerizationand by direct degradation of high molecular weight PTFE. The propertiesof several of these are summarized in the table below. Average PrimarySpecific HOSTA- Bulk Particle Particle Surface FLON ™ Density Size (μm)Size (nm) Area (m²/g) TF (g/L) (Laser (Laser (BET Nitrgoen micropowder(ISO 12086)) Diffraction) Diffraction) Absorption) TF 9201 350 6 200 10TF 9202 300 4 190 11 TF 9205 400 8 —  2 TF X 9207 280 4 120 17

[0055] In one embodiment, the PTFE homopolymer has a bulk densityranging from about 250 to about 500 g/L (grams per liter) as measured bystandard test method ISO 12086 or ASTM D4894.

[0056] In one embodiment, the weight ratio of the reaction product ofthe amine and the carboxylic acid (component (a)) to the fluoropolymer(component (b)) ranges from about 70:30 to about 99:1, and in oneembodiment from about 80:20 to about 95:1 and in one embodiment fromabout 85:15 to about 95:1.

[0057] The Powder Coating Composition

[0058] Powder coating compositions are well known to those skilled inthe art. They are coating compositions made almost entirely from solidcomponents. Although in such a composition, there might be a fewcomponents that might be in the form of a liquid, the composition as awhole is in the form of a powder. The word “powder” here is meant toinclude not only materials with a very small particle size (less thanabout 10 micron) but also those with larger sizes, such as granules andother particulate matter. Typically, the particle size of a powercoating composition will vary from 0.3 to 300 microns, more commonlyfrom 0.3 to 105 microns. Powder coatings were developed in response to arecognized need and desire by the coatings industry to reduce energyconsumption and solvent emission.

[0059] Film-Forming Resin Composition

[0060] One component of the present powder coating composition is a filmforming resin composition. The words “film forming resin composition”include the complete system of:

[0061] 1) a polymer (also called resin or “binder”) that is capable offorming a film (the “film-forming resin”) either with a curing agent(also known as crosslinking agent, curative, crosslinker or hardener) orwithout a curing agent (such as by air-drying or by the application ofheat);

[0062] 2) a crosslinking agent, if necessary;

[0063] 3) any catalyst or accelerator that may be necessary tofacilitate the reaction between the film forming resin and thecrosslinking agent.

[0064] Polymers which can be employed as the film forming resin includeoil-free polyester resins, acrylic resins and epoxy resins.

[0065] As the words “film forming resin composition” include anycurative (crosslinking agent) that may be used for crosslinking, theaforementioned resins also intrinsically include urethane resins whichform when a di-or polyisocyanate group (—NCO—) bearing intermediate(such as an isocyanate curative) reacts with a di- orpolyhydroxyl-bearing species. The species used to react with theisocyanate functionality can be described as any hydrogen donor bearingtwo or more active hydrogens. Although there is a large array ofhydrogen donors for use by the paint chemist in the preparation ofpolyurethane coatings, hydroxyl-based systems are especially useful.Useful hydroxyl-based systems include hydroxylated acrylics,hydroxylated (saturated) polyesters, epoxies and other polyether-basedpolyols, polycaprolactone-based polyols, castor oil derivatives, andpolyamides, phenolics and amino systems. Useful isocyanate-terminatedspecies include the aliphatics, hexamethylene diisocyanate andisophorone diisocyanate and the aromatic species, toluene diisocyanateand diphenylmethyl diisocyanate.

[0066] The film-forming resin can be a thermoplastic resin or athermosetting resin. Thermoplastic resins do not chemically react uponthe application of heat but melt and flow over the part to be coated.Upon cooling, the film hardens can be remelted again by the simpleapplication of heat. Thermosetting resins are reactive systems, and achemical reaction—crosslinking—takes place between the resin and ahardener (crosslinking agent) molecules upon application of heat. Thisleads to a cured or hardened film which can no longer be melted uponreheating. Thermosetting resins also include water curing systems, suchas moisture curing urethanes.

[0067] Suitable examples of thermoplastic resins for powder coatingcompositions include polyolefins, including low density polyethylene(LDPE) and polypropylene, polyvinylchloride (PVC), polyamides,polyesters, chlorinated polyethers, and cellulose-acetobutyrate.

[0068] What follows is a brief description of some of the film formingresins which may be used in accordance with this invention. A briefdescription of the curatives and/or curing reactions is also includedwhen the resin is also used as a thermosetting resin.

[0069] The film forming resins that are useful include epoxy resins.These include any one of a number of well known organic resins which arecharacterized by the presence therein of the epoxide group

[0070] A wide variety of such resins are available commercially. Suchresins have either a mixed aliphatic-aromatic or an exclusivelynon-benzenoid (i.e., aliphatic or cycloaliphatic) molecular structure.

[0071] Examples of epoxy resins that can be used include diglycidylether of bisphenol A (DGEBA; made by reacting epichlorohydrin withbisphenol A); further reaction products of DGEBA with additionalbisphenol A to yield solid, linear and difunctional epoxy resins; andepoxy novolac resins. The epoxy resins can be crosslinked with a varietyof hardeners or curing agents to yield coatings with excellent adhesion,good mechanical and physical properties, and very good corrosionresistance. These curing reactions include epoxy-amine reactions,epoxy-phenolic reactions, epoxy-anhydride reactions, epoxy-carboxylreactions, and epoxy-epoxy reactions.

[0072] The film forming resins also include oil-free polyester resins.The words “polyester resin” will henceforth be used to refer to anoil-free polyester resin and is to be distinguished from an unsaturatedpolyester resin. Polyester resins are the reaction products ofmultifunctional alcohols (such as glycols) with multifunctional acids oracid anhydrides. The ratio of multifunctional alcohol to acid or acidanhydride determines the type of reactive end-group, i.e., an excess ofglycol will result in hydroxy terminated (or hydroxy functional)polyesters whereas an excess of acid or acid anhydride will result in acarboxyl terminated (or carboxy functional) polyester. Useful startingmaterials as far as the acidic portion is concerned include terephthalicacid, isophthalic acid, maleic anhydride, trimellitic anhydride, andadipic acid. Useful multifunctional alcohols include ethylene glycol,diethylene glycol, 1,4-butanediol, trimethylolpropane, andneopentylglycol. For thermosets (thermosetting resins), curing agentsfor hydroxy functional polyesters include blocked isocyanates. Thealiphatic hydroxyl groups of the OH-functional polyester can react withisocyanates as shown in Scheme 1 below:

[0073] Since this reaction occurs readily at room temperature, it isnecessary to block one of the two reactants and this is normally theisocyanate group. A useful blocking agent is ε-caprolactam. Usefulisocyanates include toluene diisocyanate (TDI), 4,4′-diphenylmethanediisocyanate (MDI), 1,6-hexamethylene diisocyanate (HMDI) and isophoronediisocyanate (IPDI). In some instances, however, these compounds areconsidered to be toxic; it is therefore preferable to form an adduct ofthe diisocyanate with a triol such as trimethylol propane or a diol suchas ethylene glycol. This can be done by reacting an excess of thediisocyanate with the alcohol to form an isocyanate terminated adduct,as exemplified in Scheme 2 below.

[0074] This in turn can be blocked with ε-caprolactam to yield theidealized structure shown in Scheme 3 below:

[0075] The reactive isocyanate group can be freed during curing andreact with the aliphatic hydroxyl groups of the polyester since theε-caprolactam is released at temperatures above about 160° C.

[0076] Other blocking agents for isocyanates (such as ketoximes) can beused provided the blocked isocyanate is in solid state at roomtemperature.

[0077] The crosslinking agents useful for the present invention alsoinclude those that are self-blocked (“blocked agent free”) isocyanateshaving a uretdione linkage. Examples of these self-blocked isocyanatecrosslinking agents include those available from Hüls America under thetradename “VESTAGON™ BF-1540”, having an average equivalent weight ofabout 280 and an isocyanate content (% NCO) of about 14.7 to about 16.7.This crosslinking agent is described as a VESTANAT™ IPDI (isophoronediisocyanate) adduct, which has internally blocked structures. As aresult, no blocking agent is liberated during curing. The product can beprocessed up to the unblocking temperature of greater than about 160° C.

[0078] In one embodiment of the present invention, the film formingresin composition comprises a polyester resin and anisocyanate-containing curative. That is, a hydroxy-functional polyesteris reacted with a blocked isocyanate to result in a polyurethane. In oneembodiment, the hydroxy-functional polyester has a hydroxy equivalentweight of about 1400 (a hydroxyl number of about 40) and an acid numberof about 13. It is available from the Ruco Polymer Corporation under thename “RUCOTE™ 102”. In one embodiment, the hydroxy-functional polyesterhas a hydroxy equivalent weight of about 1870 (a hydroxyl number ofabout 30) and an acid number of about 5. It is available from the RucoPolymer Corporation under the name “RUCOTE™ 112”. The isocyanatecuratives typically include blocked isocyanates which are solids. In apreferred embodiment, the blocked isocyanate is an ε-caprolactam blockedisophorone isocyanate adduct. It has an equivalent weight of about 280and is marketed by Ruco Polymer Corporation under the name “RUCOTE™NI-2”.

[0079] For carboxy functional polyesters, the curing agents includesolid polyepoxides and β-hydroxyalkylamides. Useful solid polyepoxide inpowder coatings include triglycidyl isocyanurate (TGIC) produced fromthe reaction between epichlorohydrin and cyanuric acid. The curingmechanism is believed to involve the reaction of the epoxy group withthe carboxyl group at elevated temperatures. A base catalyst issometimes used to accelerate the reaction. Tetrafunctionalβ-hydroxyalkylamides are believed to crosslink via simple esterificationreaction with the elimination of water.

[0080] In one embodiment of the present invention, the film formingresin composition comprises an epoxy-polyester hybrid resin. The epoxycomponent of the hybrid can be a bisphenol A based epoxy resin having anepoxy equivalent weight of 730 to 820. It is a “type 3-3.5” resin havingon average 3-3.5 hydroxyl-substituted propoxy bisphenol A units (n=3-3.5on average in structure below):

[0081] This epoxy resin is available from Dow Chemical Company under thename “D.E.R.™ 663U”. The polyester resin in this epoxy-polyester hybridis believed to be a saturated carboxylated (i.e. carboxy-functionalized)polyester resin, having an acid number of 70 to 85, and a glasstransition temperature of about 56° C. This polyester resin is availablefrom DSM Resins BV under the name “URALAC™ P 5127”. The curing reactionfor this epoxy-polyester hybrid is believed to involve epoxy-carboxylreactions, where the carboxyl terminated polyester cures the epoxyresin. The reaction between and epoxy group and a carboxylic acid groupproceeds readily at elevated temperatures, producing ester and hydroxyfunctionalities. This reaction sometimes utilizes a suitable catalyst. Acommonly employed catalyst is benzyltrimethylammonium chloride. Othercompounds such as 2-methylimadazole can also be used as a catalyst forthe curing reaction.

[0082] Another class of resins that can be used in the present inventionare the acrylic resins which are obtained by polymerizing a suitablecombination of a functional group-containing monomer and anothercopolymerizable monomer in an ordinary manner. The polymerizationreaction is usually initiated by free radical generators such as benzoylperoxide or azobisisobutyronitrile (AIBN) and the reaction is afour-part process with the following steps occurring at different rates:(1) Initiation, (2) Propagation, (3) Chain transfer, and (4)Termination. The polymerization temperature is ordinarily between 60° C.and 100° C. and polymerization time is usually 3 to 10 hours. Examplesof the functional group-containing monomers include hydroxylgroup-containing monomers such as beta-hydroxyethyl acrylate,beta-hydroxypropyl acrylate, beta-hydoxyethyl methacrylate,beta-hydroxypropyl methacrylate, N-methylol acrylamide and N-methylolmethacrylamide; carboxyl-group containing monomers such as acrylic acid,methacrylic acid, itaconic acid, maleic acid, fumaric acid, as well asmonoesters of maleic acid and fumaric acid with monoalcohols; alkoxylgroup-containing monomers such as N-butoxy-methylmethacrylamide andN-butoxymethylacrylamide; and epoxy group-containing monomers such asglycidyl methacrylate, glycidyl acrylate and allyl glycidyl ether. Thesemonomers may be used either alone or in the form of a combination of twoor more of them. The functional group-containing monomer is used in anamount of about 5 to about 40% by weight of total monomers. Examples ofthe monomers copolymerized with these functional group-containingmonomers include olefinically unsaturated monomers such as ethylene,propylene and isobutylene, aromatic monomers such as styrene,vinyltoluene and alphamethylstyrene; esters of (meth)acrylic acid andalcohols of 1 to about 18 carbon atoms such as methyl(meth)acrylate,ethyl (meth)acrylate, propyl(methacrylate), n-butyl(meth)acrylate,isobutyl(meth)acrylate, cyclohexyl(meth)acrylate,2-ethylhexyl(meth)acrylate and lauryl(meth)acrylate; vinyl esters ofcarboxylic acid of 2 to 11 carbon atoms such as vinyl acetate, vinylpropionate and vinyl 2-ethylhexanoate; as well as vinyl chloride,acrylonitrile and methacrylonitrile. They may be used either alone or inthe form of a mixture of two or more.

[0083] Acrylic resins useful for thermosetting powder coatings generallyhave glass transition temperatures (T_(g)) above about 65° C. andmelting ranges between 70-110° C. to ensure the necessary physicalstability and ease of application. In addition to this, they generallypossess reactive groups so that they can be crosslinked afterapplication to the substrate. Two types of acrylic resins have beendeveloped to fulfill these requirements, namely hydroxy functionalacrylic resins that can be crosslinked with blocked isocyanates andepoxy functional acrylic resins that can be crosslinked with acrystalline dibasic aliphatic acids such as docanedicarboxylic acid anddodecanedicarboxylic acid.

[0084] In one embodiment of this invention, the film forming resincomposition (a) comprises an acrylic-epoxy hybrid resin. In oneembodiment, the acrylic component of this hybrid resin is a saturatedcarboxylated acrylic resin. In one embodiment this acrylic resin has acarboxy equivalent weight of about 750, an acid number of about 75, amolecular weight of about 17000, and a glass transition temperature(T_(g)) of about 57° C. It is available from S. C. Johnson Polymer underthe name “SCX 819”. This carboxylated acrylic resin can crosslink withepoxy resins based on Bisphenol A or with other acrylic resins based onglycidyl methacrylate.

[0085] In one embodiment of the present invention, the film formingresin composition (a) comprises a saturated hydroxy-functional acrylicresin. In one embodiment, this hydroxy functional acrylic resin has ahydroxy equivalent weight of about 600, a molecular weight of about18,000, a glass transition temperature (T_(g)) of about 50° C. and ahydroxyl number of about 94. It is available from S. C. Johnson Polymerunder the name “JONCRYL™ 587”. This acrylic resin can be cured with anisocyanate containing curative such as a blocked isophorone diisocyanateadduct.

[0086] In one embodiment, the film forming resin composition comprisesan acrylic-polyester hybrid resin. The acrylic -polyester hybrid resincomprises an acrylic resin such as the aforementioned hydroxy functionalacrylic resin and a carboxylated polyester resin. The acrylic-polyesterhybrid system can also be cured with an isocyanate containing curingagent such as a blocked isophorone diisocyanate (IPDI) adduct.

[0087] As already mentioned above, catalysts or accelerators may be usedto increase the rate of reaction between a resin and a hardener and areincluded within the film forming resin composition. They are usuallyadded at levels between 0.1 to 1.0% and can be used to either reduce thecuring time at a given temperature or alternatively, reduce the curingtemperature. The catalyst employed depends on the film forming resin andthe hardener. Typical catalysts include imidazoles, cyclic amidine,alkyl/aryl ammonium halides, and zinc alkyl/aryl thiocarbamates.

[0088] The concentration of the film forming resin composition in thepowder coating composition will vary depending on whether the powdercoating composition is a pigmented or clear (i.e. not having anypigments) system. Typically, the concentration of the film forming resincomposition will be 45 to 95%, more preferably 60 to 90% by weight basedon the total weight of the powder coating composition.

[0089] The Additive Composition

[0090] The second major component of the powder coating composition ofthis invention is the non-flatting and slip-enhancing additivecomposition. The words “non-flatting and slip-enhancing amount” denoteany amount of the additive composition (b) that is sufficient to providethe inventive powder coatings with non-flatting and slip-enhancingproperty. In one embodiment the additive composition (b) is present at alevel of at least about 0.01% by weight of the coating composition. Inone embodiment, it is present at a level of about 0.01 to about 5%; inone embodiment about 0.1 to about 3%; and in one embodiment about 0.2 toabout 2% by weight of the coating composition.

[0091] The words “non-flatting” denote that the additive composition (b)when incorporated in a coating composition is able to retain at leastabout 75% of the initial gloss. The words “initial gloss” denote thegloss of the cured coating composition without the additive composition(b). Gloss is usually measured according to test method ASTM D-523. Inone embodiment, at least about 85% of the initial gloss is retained. Inone embodiment, at least about 95% of the initial gloss is retained. Inone embodiment, the gloss is enhanced compared to the initial gloss.

[0092] The words “slip-enhancing” denote that a cured powder coatingcomposition containing the additive composition (b) has an improved(i.e. lower) coefficient of friction compared to a powder coatingcomposition without the additive composition (b). Coefficient offriction measurements are usually made according to test method ASTMD-4518. The additive composition (b) of the present invention is a blendof (i) the non-crosslinked reaction product made by reacting an organicalcohol and a carboxylic acid or a reactive equivalent of saidcarboxylic acid, and (ii) a fluoropolymer.

[0093] The additive composition of this invention is usually present ata level of at least about 0.01% by weight of the coating composition. Inone embodiment, it is present at a level of about 0.01 to about 5%, andin one embodiment about 0.1 to about 3%, and in one embodiment about 0.2to about 2% by weight of the coating composition.

[0094] Other Optional Components of the Powder Coating Composition

[0095] The powder coating compositions of this invention can alsocontain other additives, such as flow control additives, deaeratingagents, pigments, fillers, and special effect additives.

[0096] Flow control additives are another component of a powder coatingcomposition. In most (though not all) formulations, this component ishighly desirable, as without it, it is very difficult to obtain curedfilms with good flow and appearance and without craters or other surfacedefects. The flow control additives can be a solid or a liquid; howeverthey normally consist of highly viscous liquids based on polyacrylates.They are supplied either in the form of so-called master batches, i.e.,they have been added to the resin by the resin manufacturer right afterthe resin cooking cycle and just prior to flaking, or the additive isabsorbed on finely divided silica and can be added to the powder premixdirectly. Thus even though this component by itself, can be a liquid,the powder coating composition as a whole is in the form of a powder.

[0097] The powder coating composition of the present invention can alsocontain a deaerating agent, such as benzoin. Benzoin is said to act asan anti-pinholing agent and as a degassing aid, and it is generallybelieved that it improves the appearance of the cured coating.

[0098] Pigments can be defined as finely ground materials which areinsoluble in the medium (binder) to be used and which provide color andhiding power to the coatings. Pigments can also influence many otherimportant properties of the finished coating such as water permeability,flexibility and impact resistance.

[0099] Pigments can generally be divided into inorganic and organicpigments. Inorganic pigments include titanium dioxide, iron oxide,chromium oxide and carbon black. Organic pigments include blue pigments,such as copper phthalocyanine blue, indanthrone blue, carbozole violet;red pigments, such as cadmium red, quinacridone red, and thioindigo red;yellow pigments such as benzidine yellow, and benzimidazolone yellow;orange pigments, such as benzidine orange, green pigments, such ascopper phthalocyanine green; and violet pigments such as quinacridoneviolet.

[0100] One or several pigments can be used in a powder coatingformulation. The details of the use of pigments are well-known to thoseskilled in the art.

[0101] Fillers, also called extenders, are chemically inert materialsthat are insoluble in the binder to be used and which impart certainproperties to the coating. Fillers can lower the cost of a final coatingcomposition, and also affect such properties and gloss, flexibility,flow characteristics, storage stability, density and porosity. Some ofthe most commonly used fillers include lithopone, barium sulfate,silicates and calcium carbonates.

[0102] The powder coating composition can also include certain specialeffect additives. Special effects such as metallic finishes, hammertonefinishes, and textured or structured finishes are, generally, moredifficult to achieve with powder coatings than with conventional liquidcoatings. Textured finishes can be obtained by the incorporation ofcertain inert additives such as polypropylene, nylon, and some specialwaxes. Hammertone finishes are achieved by the incorporation of acontaminant that competes against the flow of the resin system used. Infact, the cured coating can have many craters and in the presence of analuminum pigment the hammertone effect will appear. Metallic finishesare difficult to achieve in powder coatings due to the lack oforientation effects of pigments or filler particles (due to very highviscosities during film formation). They can also be quite hazardous dueto the combustible nature of the metallic pigments. Methods toincorporate metallic pigments to give a metallic finish to coatingsinclude incorporation prior to the extrusion process, post-blending tothe finished powder coating, and a special bonding process during whichthe metallic pigments are bonded to the surface of the powder particlesafter they have been ground.

[0103] Application methods for powder coatings are known to thoseskilled in the art. They include the fluidized bed method, electrostaticfluidized bed method, electrostatic spray method, triboelectric spraymethod, use of internal and external corona guns, powder bells andpowder rotary atomizers, the preferred method being the use of coronaguns.

[0104] Furthermore, the general manufacturing process for powdercoatings is also familiar to those skilled in the art, and include thestages of premixing, melt-mixing (extruding), and pulverizing.

[0105] In one embodiment, the components of the present powder coatingcomposition are melt-mixed in an extruder into a homogeneous melt, andthe melt is subsequently cooled and ground into a powder. The purpose ofthe melt mixing process or extrusion process in general is to distributethe various additives like pigments, fillers, catalysts, hardeners, flowagents, etc., of a powder coating composition as homogeneously aspossible in the resin system. This melt mixing process can be done by anextruder. The resin and other components of the powder coatingcomposition (such as additives, pigments, and flow agents) are meltedand mixed into a homogeneous melt in the extruder. The resulting meltcan subsequently be cooled and ground into a fine powder. The resultingpowder can then be spray applied to a substrate using electrostaticpowder spraying apparatus.

[0106] The homogeneous melt mixing process is to be distinguished fromthe “dry blending” process, which latter involves mixing together allthe components of the powder coating composition under “dry” conditions.(It is to be noted however, that some components can be melt-mixed priorto a dry blending process. In this case the dry blending will mix theprior melt-mixed components with other components. For example, someliquid additives like flow agents are melt-mixed onto one of the solidcomponents prior to a dry blending operation.). The energy generatedduring the dry blending operation may be sufficient to warm the resin toits glass transition temperature (T_(g)). The granules of the resin mayswell and the other ingredients (such as other additives and pigments)may stick to the outside of the resin granules. The resulting mixturecan then be cooled to room temperature.

[0107] Dry blended powders, being generally made of larger granules thathave other components embedded in the surface of the granules generallybehave differently than an extruded, melt mixed homogeneous powdercoating composition. A present powder coating composition where theadditive composition is dry blended with the rest of the components ofthe powder coating composition will tend to have the additive on thesurface of the granules. A melt mixed homogeneous powder coatingcomposition, however has the additive homogenized into a polymer melt.Thus, there can be compositional differences between a melt mixedhomogeneous powder coating composition and a dry blended powder coatingcomposition. As a result, a powder coating composition which has theadditive composition of the present invention dry blended with the restof the components (such as resin composition, pigments, fillers, andflow agents) is expected to cause more surface defects than a powdercoating composition where the additive composition is melt mixed withthe other components in an extruder to give a homogeneous powder coatingcomposition.

[0108] Furthermore, powder coating compositions wherein the componentsof the powder coating composition are mixed by dry blending aregenerally not suited for electrostatic applications as the powdergranules are too large. In general, high gloss thin film coatings arenot usually achieved in a powder coating application where thecomponents of the coating composition are mixed by dry blending. Suchdry blended compositions are generally suited for fluidized bedapplications wherein preheated substrates are dipped into a fluidizedbed containing the powder coating composition for application of thecoating composition onto the substrate. Substrates coated by this(fluidized bed) method generally do not have thin film or high glosscoatings, as controlled film builds are generally very difficult toachieve by this method of coating. On the other hand, melt-mixedextruded homogeneous powder coating compositions can be easily sprayapplied to a substrate using electrostatic powder guns, and the coatedsubstrate can have controlled thickness as the powder is finer and it iseasier to control the application of the powder coating composition ontothe substrate.

[0109] The substrates for powder coatings include metal, wood andplastic, and glass. Examples of substrates that have been powder coatedindustrially include office furniture, appliances (such asrefrigerators, freezers, washing machines) as well as automotive bodypanels.

[0110] The temperature used to heat the applied powder coatingcomposition on suitable substrates to form the film varies depending onwhether the coating composition is a thermoplastic or thermosettingsystem, with higher temperature being applied for curing the thermosets.The temperature for melting the coating composition ranges from 70 to90° C. (for thermoplastics and thermosets); for curing of thermosets,the temperature is further raised to 150-200° C. The film thickness ofthe coating ranges from 10-500 microns (0.5-20 mils), more preferably10-250 microns (0.5-10 mils). The cured coatings with the additive arenon-flatting and have enhanced slip properties compared to coatingswithout the additive.

[0111] An excellent source describing the chemistry, uses andapplications of various resins and additives used in coatings isProtective Coatings—Fundamentals of Chemistry and Compositions by CliveH. Hare, Technology Publishing Company, Pittsburgh, Pa. (1994).

[0112] A particularly excellent source describing the chemistry,manufacture, and application of powder coatings is Powder Coatings byJosef H. Jilek, published by Federation of Societies for CoatingsTechnology, Darlene Brezinski & Thomas J. Miranda, Eds.(1993).

EXAMPLES Example 1 Evaluation of a Blend of Sorbitan Tristearate andPolytetrafluoroethylene (PTFE) In a Polyester Resin/Isocyanate CurativePowder Coating Formulation

[0113] Tables 1 shows a polyester resin/isocyanate curative powdercoating formulation used in the evaluation of the blend of sorbitantristearate and PTFE as the additive composition of this invention.TABLE 1 Polyester Resin/Isocyanate curative based Powder coatingformulation used in evaluation of an additive composition. Raw MaterialTrade A Name (Control) B C Ruco ™ 102¹ 56.86 56.01 56.01 Ruco ™ NI-2²9.74 9.59 9.59 Uraflow ™ B³ .40 .40 0.40 Resiflow ™ P67⁴ 1.0 1.0 1.0Blanc Fixe Micro⁵ 30.0 30.0 30.0 Sorbitan tristearate — 1.0 — Blend ofsorbitan tristearate — — 1.0 (90%) and PTFE (10%) Special Black #4⁶ 2 22

[0114] The performance results are shown in Table 2. TABLE 2 TestResults of Powder Coating Compositions of Table 1 A Test Measurements(Control) B C gloss (60°) (ASTM D523) 87 87 86-87 gloss (20°) (ASTMD523) 48-50 57-60 54-55 DOI (Distinction of Image) 30 41 41 (ASTME430-91 & E284) Color CIELAB — −0.19 −0.51 Spectral included (ASTMD2244-93) DL Da — −0.03 −0.04 Db — 0.08 0.18 DE — 0.16 0.41 Appearance(Visual) OK OK OK Film build (mils) 1.4-2.0 1.1-2.0 1.1-1.9 Coefficient.of Friction (D4518) Max static 0.1306 0.0551 0.0724 (Dynamic) Ave.0.1144 0.0690 0.00681 Standard deviation. 0.0110 0.0061 0.0028

[0115] Processing:

[0116] Premix-30 secs. wearing blender

[0117] Extruding: Baker-Perkins APV MP19PC 15:1 twin screw extruder

[0118] Barrel 90° C. Zone 1; 110° C. Zone 2; RPM=350; Feeder 25; Rolls21.9

[0119] Components were ground using bench top grinder, sieved through a140 mesh screen, and sprayed using Nordson Versaspray II powder spraygun.

[0120] Substrate: Phosphate coated cold rolled steel panel-Bonderite1000 Parkalene 60 deionized water rinsed, unpolished

[0121] Cure: 15 minutes @ 191° C. (375° F.) in precision electric oven

[0122] Compared to the control formulation without any slip additive(formulation A), the results with the blend of sorbitan tristearate andPTFE (formulation C) in the above Polyester resin/Isocyanate curativeformulation show improved 20° gloss, equivalent 60° gloss, and improvedslip properties (lower coefficient of friction). Compared to theformulation with the sorbitan tristearate (formulation B), thecomposition with the blend of sorbitan tristearate and PTFE (formulationC) shows equivalent 60° gloss, slightly lower 20° gloss and equivalentdynamic coefficient of friction.

[0123] However, an additional advantage of the blend over the sorbitantristearate itself can be seen in results of a cardboard mar double rubtest. This test measures the anti-mar/anti-scratch property of a coatingcomposition.

[0124] The procedure for this test is as follows: A new, unusedcardboard box is cut out into several strips that are 1.5 inches wideand 6-8 inches long. A strip of the cardboard back is folded upon itselfuntil the two halves meet together which leaves a sharp edge at thebend. The folded cardboard is placed against the metal panel to betested with the sharp bend toward the coating's surface. Using handpressure only, the cardboard is rubbed across the surface of the coatingin the direction of the wide part of the cardboard. One (1) strokedouble rub consists of a back and forth motion across the panel. Thenumber of double rubs that it takes to produce scratches that are easilyseen with the unaided eye are reported.

[0125] The results of this test is shown in table 3. TABLE 3 CardboardMar Double Rub Test Results A (Control) B C # Strokes to 40 40 80scratch

[0126] The data of table 3 indicate that composition C containing theblend of PTFE and sorbitan tristearate performs better as aanti-mar/anti-scratch composition than either the composition containingsorbitan tristearate alone, or the composition without any additive.

Example 2 Evaluation of an Additive Composition In a Epoxy-PolyesterHybrid Resin Based Powder Coating Formulation

[0127] Table 4 shows an epoxy-polyester hybrid resin based powdercoating formulation used in evaluating an additive composition of thepresent invention. TABLE 4 Epoxy-Polyester Hybrid based Powder CoatingFormulation used in the evaluation of An Additive Composition. RawMaterial Trade A Name (Control) B C D Uralac ™ P 5127¹ 33.6 33.6 33.633.6 D.E.R. 663U² 33.6 33.6 33.6 33.6 Blanc Fixe F³ 30.4 30.4 30.4 30.4Special Black #4⁴ 1.0 1.0 1.0 1.0 Lanco-Flow ™ P10⁵ 1.0 1.0 1.0 1.0Benzoin⁶ 0.4 0.4 1.0 1.0 Sorbitan tristearate — 1.0 — — (micronized)Sorbitan tristearate — — 1.0 — (flakes) Blend of sorbitan 1.0tristearate (89%) and PTFE (11%)

[0128] Performance results are shown in Table 5. TABLE 5 Test Results ofPowder Coating Compositions of Table 4 A Test Measurements (Control) B CD gloss (60°) (ASTM D523) 100 93 94 95 gloss (20°) (ASTM D523) 89 78 8283 Coefficient of Friction 0.215 0.080 0.095 0.080 (Dynamic) (ASTMD4518)

[0129] Processing:

[0130] Premixing—Powder coating components were weighed up and mixed ina bag.

[0131] Extruding—All materials were extruded twice with a “APV 19PC”twin screw extruder with a barrel length of 15L/D at followingparameters:

[0132] Barrel zone 1: 60° C.

[0133] Barrel zone 2: 100° C.

[0134] melting temperature: 70-75° C.

[0135] screw r.p.m.: 300

[0136] torque: 60-70%

[0137] Grinding—After crushing, the samples were ground with a RetschZ-100 mill. Then the coatings were sieved with a 100 μm sieve.

[0138] Application—The coatings were sprayed with apowder-manual-pulverizing tool on aluminum panels by the Corona-method:

[0139] Voltage: 80 KV

[0140] Delivery air: 1.2 bar

[0141] Curing—The panels were cured at 160° C. for 18 minutes.

[0142] In the Epoxy-Polyester blend formulation, the results ofcomposition D, containing the blend of PTFE and sorbitan tristearateshow the best overall results (performing better than compositions B andC) as a nonflatting slip-enhancing composition. This composition has thelowest coefficient of friction while retaining most of the initialgloss.

[0143] Each of the documents referred to above is incorporated herein byreference. Unless otherwise indicated, each chemical or compositionreferred to herein should be interpreted as being a commercial gradematerial which may contain the isomers, by-products, derivatives, andother such materials which are normally understood to be present in thecommercial grade. However, the amount of each chemical component ispresented exclusive of any solvent or diluent oil which may becustomarily present in the commercial material, unless otherwiseindicated. It is to be understood that the amount, range, and ratiolimits set forth herein may be combined.

[0144] While the invention has been explained in relation to itspreferred embodiments, it is to be understood that various modificationsthereof will become apparent to those skilled in the art upon readingthe specification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

What is claimed is:
 1. A composition comprising: (a) at least onenon-crosslinked product made by the reaction of an alcohol and acarboxylic acid or a reactive equivalent of said carboxylic acid; saidproduct comprising at least one ester functionality and at least onehydrocarbyl group of about 10 to about 100 carbon atoms; and (b) atleast one fluoropolymer.
 2. The composition of claim 1 wherein incomponent (a), the alcohol comprises 2 to about 10 hydroxyl groups. 3.The composition of claim 1 wherein in component (a), the alcohol isselected from the group consisting of ethylene glycol, glycerol,pentaerythritol, and mixtures of two or more thereof.
 4. The compositionof claim 1 wherein in component (a), the alcohol is selected from thegroup consisting of inositol, sorbitol, mannitol, ribitol, and mixturesof two or more thereof.
 5. The composition of claim 1 wherein incomponent (a), the alcohol is sorbitol.
 6. The composition of claim 1wherein in component (a), the alcohol is sorbitan.
 7. The composition ofclaim 1 wherein in component (a), the carboxylic acid contains 1 toabout 10 carboxyl groups.
 8. The composition of claim 1 wherein incomponent (a), the carboxylic acid contains about 10 to about 100 carbonatoms.
 9. The composition of claim 1 wherein in component (a), thecarboxylic acid is stearic acid.
 10. The composition of claim 1 whereinin component (a), the alcohol is glycerol and the carboxylic acid isstearic acid.
 11. The composition of claim 1 wherein in component (a),the alcohol is ethylene glycol and the carboxylic acid is stearic acid.12. The composition of claim 1 wherein in component (a), the alcohol ispentaerythritol and the carboxylic acid is stearic acid.
 13. Thecomposition of claim 1 wherein in composition (a), the reaction productcomprises glycerol distearate.
 14. The composition of claim 1 wherein incomposition (a), the reaction product comprises ethylene glycoldistearate.
 15. The composition of claim 1 wherein in composition (a),the reaction product comprises pentaerythritol tetrastearate.
 16. Thecomposition of claim 1 wherein in composition (a), the reaction productcomprises a sorbitan ester.
 17. The composition of claim 16 wherein thesorbitan ester comprises a sorbitan fatty acid ester, the fatty acidcomponent of said ester comprising a carboxylic acid of about 10 toabout 100 carbon atoms.
 18. The composition of claim 17 wherein thefatty acid comprises a carboxylic acid of about 12 to about 24 carbonatoms.
 19. The composition of claim 16 wherein the sorbitan estercomprises a sorbitan stearate, a sorbitan oleate, or a mixture thereof.20. The composition of claim 19 wherein the sorbitan stearate issorbitan tristearate.
 21. The composition of claim 16 wherein thesorbitan ester comprises a polyoxyalkylene sorbitan ester wherein thealkylene group has about 2 to about 24 carbon atoms.
 22. The compositionof claim 21 wherein the alkylene group of the polyoxyalkylene sorbitanester is selected from the group consisting of ethylene, propylene,butylene and mixtures of two or more thereof.
 23. The composition ofclaim 1 wherein the fluoropolymer (b) comprises tetrafluoroethylenerepeat units.
 24. The composition of claim 1 wherein the fluoropolymer(b) is polytetrafluoroethylene.
 25. The composition of claim 24 whereinthe bulk density of the polytetrafluoethylene varies from about 250 toabout 500 g/L.
 26. The composition of claim 1 wherein the weight ratioof component (a) to component (b) ranges from about 70:30 to about 99:1.27. A powder coating composition, comprising: a film forming resincomposition; and a non-flatting slip-enhancing amount of an additivecomposition comprising the composition of claim
 1. 28. The compositionof claim 27 wherein the components of the powder coating composition aremelt-mixed in an extruder into a homogeneous melt, and the melt issubsequently cooled and ground into a powder.
 29. The composition ofclaim 27 wherein the film forming resin composition comprises athermoplastic resin.
 30. The composition of claim 27 wherein the filmforming resin composition comprises a thermosetting resin.
 31. Thecomposition of claim 27 wherein the film forming resin compositioncomprises a resin selected from the group consisting of epoxy resins,oil-free polyester resins, acrylic resins, and mixtures of two or morethereof.
 32. The composition of claim 27 wherein the film forming resincomposition comprises an oil-free polyester resin and anisocyanate-containing curative.
 33. The composition of claim 32 whereinthe isocyanate-containing curative is an ε-caprolactam blockedisophorone diisocyanate.
 34. The composition of claim 27 wherein thefilm forming resin composition comprises an epoxy-polyester hybridresin.
 35. The composition of claim 34 wherein the epoxy-polyesterhybrid resin comprises a type 3-3.5 bisphenol A epoxy resin.
 36. Thecomposition of claim 8 wherein the epoxy-polyester hybrid resincomprises a saturated, carboxylated polyester resin.
 37. The compositionof claim 27 wherein the film forming resin composition comprises anacrylic-epoxy hybrid resin.
 38. The composition of claim 37 wherein theacrylic-epoxy hybrid resin comprises a saturated, carboxylated acrylicresin.
 39. The composition of claim 27 wherein the film forming resincomposition comprises an acrylic-polyester hybrid resin and an isocyatecontaining curative.
 40. The composition of claim 39 wherein theacrylic-polyester hybrid resin comprises a saturated, hydroxy functionalacrylic resin.
 41. The composition of claim 27 wherein the additivecomposition is present at a level of at least about 0.01% by weight ofthe coating composition.
 42. The composition of claim 27 furthercomprising: (c) a flow control agent (d) a deaerating agent; and (e) apigment.
 43. The composition of claim 42 wherein components (a), (b),(d), and (e) of said composition are in the form of a solid, andcomponent (c) is in the form of a solid or liquid.
 44. The compositionof claim 42 wherein component (c) is in the form of a liquid.
 45. Thecomposition of claim 42 wherein component (c) is in the form of a solid.46. A powder coating composition comprising: (a) a film forming resincomposition selected from the group consisting of oil-free polyesterresins containing isocyanate curatives and epoxy-polyester hybridresins; and (b) a non-flatting and slip-enhancing amount of an additivecomposition, comprising: (i) sorbitan tristearate; and (ii)polytetrafluoroethylene; wherein the weight ratio of (b)(i) to (b)(ii)ranges from about 70:30 to about 99:1.
 47. A method for coating asubstrate comprising the steps of: (I) applying a powder coatingcomposition on said substrate, said coating composition comprising: (a)a film-forming resin composition; and (b) a non-flatting andslip-enhancing amount of an additive composition, comprising: (i) atleast one non-crosslinked product made by the reaction of an alcohol anda carboxylic acid or a reactive equivalent of said carboxylic acid; saidproduct comprising at least one ester functionality and at least onehydrocarbyl group of about 10 to about 100 carbon atoms; and (ii) atleast one fluoropolymer; and (II) heating the applied powder coatingcomposition from step (I) to form a film.
 48. The method of claim 47wherein components (a) and (b) of the powder coating composition aremelt-mixed in an extruder into a homogeneous melt and said melt issubsequently cooled and ground into a powder.